Thread (38 messages) 38 messages, 9 authors, 2017-05-05

[kernel-hardening] Re: [PATCH v3 1/2] modules:capabilities: automatic module loading restriction

From: Ben Hutchings <hidden>
Date: 2017-04-20 15:02:44
Also in: linux-api, lkml

On Thu, 2017-04-20 at 14:44 +0200, Djalal Harouni wrote:
quoted
On Thu, Apr 20, 2017 at 4:22 AM, Ben Hutchings [off-list ref] wrote:
On Thu, 2017-04-20 at 00:20 +0200, Djalal Harouni wrote:
[...]
quoted
+modules_autoload:
+
+A sysctl to control if modules auto-load feature is allowed or not.
+This sysctl complements "modules_disabled" which is for all module
+operations where this flag applies only to automatic module loading.
+Automatic module loading happens when programs request a kernel feature
+that is implemented by an unloaded module, the kernel automatically
+runs the program pointed by "modprobe" sysctl in order to load the
+corresponding module.
+
+When modules_autoload is set to (0), the default, there are no
+restrictions.
+
+When modules_autoload is set to (1), processes must have CAP_SYS_MODULE
+to be able to trigger a module auto-load operation, or CAP_NET_ADMIN
+for modules with a 'netdev-%s' alias.
+
+When modules_autoload is set to (2), automatic module loading is
+disabled for all. Once set, this value can not be changed.
I would expect a parameter 'modules_autoload' to be a boolean, so this
behaviour would be surprising.

What is the point of mode 2???Why would someone want to set
modules_disabled=0 and modules_autoload=2?
modules_disabled is too restrictive and once set it can't be changed,
maybe that's why not all users use it.

With modules_disabled=0 and modules_autoload=2
[...]

Hmm, OK.  How about naming this modules_autoload_mode, then, so that
it's obviously not a boolean?

Ben.

-- 
Ben Hutchings
It is easier to change the specification to fit the program than vice
versa.

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